[GitHub] [shardingsphere] destiny-z opened a new issue, #16896: /dangdang/ddframe/rdb/sharding/keygen/DefaultKeyGenerator generates the same sequence in the same timestamp

[GitBox <gi...@apache.org>]

destiny-z opened a new issue, #16896:
URL: https://github.com/apache/shardingsphere/issues/16896

   we use the **shardingsphere/sharding-jdbc-core/src/main/java/com/dangdang/ddframe/rdb/sharding/keygen/DefaultKeyGenerator.java** to generate key in the production environment, but we find it will generate the same sequence in the same timestamp in the same pod.
   ![image](https://user-images.githubusercontent.com/9402157/163785601-3f44dea8-dbc0-4f36-97e4-b3c78a733d02.png)
   Here is our KeyGenerator algorithm which is the same as dangdang. The only difference is that we modified the SEQUENCE_BITS and   WORKER_ID_BITS.
   Here is the code.
   ```
   @Slf4j
   public final class KeyGenerator implements ShardingKeyGenerator {
   
       public static final long EPOCH;
   
       private static final long SEQUENCE_BITS = 6L; //原来12位
   
       private static final long WORKER_ID_BITS = 6L; //原来4位
   
       private static final long SEQUENCE_MASK = (1 << SEQUENCE_BITS) - 1;
   
       private static final long WORKER_ID_LEFT_SHIFT_BITS = SEQUENCE_BITS;
   
       private static final long TIMESTAMP_LEFT_SHIFT_BITS = WORKER_ID_LEFT_SHIFT_BITS + WORKER_ID_BITS;
   
       private static final long WORKER_ID_MAX_VALUE = 1L << WORKER_ID_BITS;
   
       @Setter
       private static TimeService timeService = new TimeService();
   
       private static long workerId;
   
       private static final Object LOCK = new Object();
   
       private Properties properties = new Properties();
   
       static {
           Calendar calendar = Calendar.getInstance();
           calendar.set(2017, Calendar.NOVEMBER, 1);
           calendar.set(Calendar.HOUR_OF_DAY, 0);
           calendar.set(Calendar.MINUTE, 0);
           calendar.set(Calendar.SECOND, 0);
           calendar.set(Calendar.MILLISECOND, 0);
           EPOCH = calendar.getTimeInMillis();
   
           initWorkerId();
       }
   
       private long sequence;
   
       private long lastTime;
   
       /**
        * Set work process id.
        *
        * @param workerId work process id
        */
       public static void setWorkerId(final long workerId) {
           Preconditions.checkArgument(workerId >= 0L && workerId < WORKER_ID_MAX_VALUE);
           KeyGenerator.workerId = workerId;
       }
   
       static void initWorkerId() {
           // 用zk生成唯一的workId
       }
   
       /**
        * Generate key.
        *
        * @return key type is @{@link Long}.
        */
       @Override
       public Comparable<?> generateKey() {
   
           synchronized (LOCK) {
               long currentMillis = timeService.getCurrentMillis();
               Preconditions.checkState(lastTime <= currentMillis,
                       "Clock is moving backwards, last time is %d milliseconds, current time is %d milliseconds", lastTime,
                       currentMillis);
               if (lastTime == currentMillis) {
                   if (0L == (sequence = (sequence + 1) & SEQUENCE_MASK)) {
                       currentMillis = waitUntilNextTime(currentMillis);
                   }
               } else {
                   sequence = 0;
               }
               lastTime = currentMillis;
               Long key = ((currentMillis - EPOCH) << TIMESTAMP_LEFT_SHIFT_BITS)
                       | (workerId << WORKER_ID_LEFT_SHIFT_BITS)
                       | sequence;
               log.info("generate key[{}] with timestamp:{}, workerId:{}, sequence:{}", key, currentMillis, workerId, sequence);
               return key;
           }
       }
   
       private long waitUntilNextTime(final long lastTime) {
           long time = timeService.getCurrentMillis();
           while (time <= lastTime) {
               time = timeService.getCurrentMillis();
           }
           return time;
       }
   }
   ```
   My concurrency is not large, but sometimes a key conflict occurs, two threads generated the same key.
   How can I fix this problem?


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[GitHub] [shardingsphere] destiny-z closed issue #16896: /dangdang/ddframe/rdb/sharding/keygen/DefaultKeyGenerator generates the same sequence in the same timestamp

[GitBox <gi...@apache.org>]

destiny-z closed issue #16896: /dangdang/ddframe/rdb/sharding/keygen/DefaultKeyGenerator generates the same sequence in the same timestamp
URL: https://github.com/apache/shardingsphere/issues/16896


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[GitHub] [shardingsphere] zjcnb commented on issue #16896: /dangdang/ddframe/rdb/sharding/keygen/DefaultKeyGenerator generates the same sequence in the same timestamp

[GitBox <gi...@apache.org>]

zjcnb commented on issue #16896:
URL: https://github.com/apache/shardingsphere/issues/16896#issuecomment-1102454518

   @destiny-z Hello, Can you try it again with` 5.1.1` version? I think you used version are too old.


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